Before a mobile telephone can be marketed, it typically must comply with maximum heating capacity guidelines imposed by governmental regulating organizations, such as the United States Federal Communication Commission (FCC) and many European regulatory organizations. For instance, in the United States and Europe, the telephone must meet various technical standards, including compliance with radio frequency exposure limits defined in terms of the specific absorption rate (SAR) of the mobile telephone. SAR is a widely accepted measurement of radio frequency energy absorbed into the body in watts per kilogram (W/kg) averaged over a certain amount of tissue when the telephone is situated close to or touching the human body.
In general, the SAR value of a mobile telephone depends on the average radiated power of the telephone, frequency (because of different antenna properties and material properties of the human tissue at different frequencies) and geometrical and mechanical configurations of the telephone. SAR values are most affected by the distance between any radiating structure to the human tissue and the average radiated power. The average radiated power depends on the communication standard utilized, and may vary within the standard depending on the traffic mode in use.